Answer:
A. They bring cool air.
Step-by-step explanation:
Jet stream is a narrow band of very strong western air currents in the atmospheres of some planets. These currents of air encircles the planet several miles in its atmosphere. In the Earth's atmosphere, there are two to three jet streams in each of the northern and southern hemispheres.
Subtropical jet streams are majorly cold fast-moving winds lying above regions of subtropical high pressure. The two classes are: subtropical jet streams and polar-front jet streams. It blows from west to east region of the earth. These air currents bring cool air to the regions it blows to.